Process of purifying sodium-sulphide solutions



Patented June 10, 1924.

UNITED STATEfi PATENT orrics.

HENRY, HOWARD, OF CLEVELAND, OHIO, ASSIGNOJR- TO THE GRASSELLI CHEMIOAL COMPANY, OF CLEVELAND, OHIO, A CORPORATION OF OHIO.

PROGESS OF IURIFYING- $DIUM-SULPHIDE SOLUTIONS.

No Drawing;

T 0 all whom it mag} concern:

Be it known that I, HENRY HowAm), a citizen of'the United States, residing at Cleveland, in the county of Cuyahoga and State of Ohio, have invented certain new anti useful Improvements in Processes of Pu ifying Sodium'Sulphide Solutions, of which the followin is a specification.

K This invention re ates to a process of making sodium sulphide and more particularly to a process of recovering sodium sulphide in marketable form from impure, dilute liquors such as are produced in the manufacture of sodium sulphide from sodium sulfate.

According to the well known method of making sodium sulphide, a material containing a sodium saltof sulfuric acid, such as salt cake, is mixed with a carbonaceous fuel nace. The product of this treatment is commonlyknown as'sodium sulphide black ash and contains varying quantities of sodium sulphide, sodium carbonate, sodium hyposulfite, sodium sulfate, unconsumed fuel, and ash. The princi al constituent of the black ash is sodium su phide the bulk of which is recovered by leaching. Ordinarily the leaching is carried out in such a Way that a strong solution of sodium sulphide is obtained and the bulk of the impurities with considerable sodium sulphide remains in the undissolved residue. This residue is then leached in order to recover the bulk of the sodium sulphide remaining in it. For this purpose leaching with a comparatively arge amount. of water is necessary and a dilute solution or liquor containing varying quantities of sodium sulphide and water soluble impurities, such as sodium carbonate, sodium h posulfite, and sodium sulfate, ispbtain'ed? Liquors such as that obtained by the above procedure have been used in various ways, usually for urposes other than the production of s ium sul hide. 'In order to re- -'cover sodium sul hi e in a substantially pure state from tie liquors it is necessary to remove or destroy the sodium carbonate content. This has been attempted by causticizing the liquors with lime but'has resulted in only a partial removal of the sodium carbonate.

and the mixture is heated in a suitable fur- Application filed March 30, 1922. Serial No. 548,186.

I have found that the removal of sodium carbonate may be rendered substantially complete if during causticiz'ation with lime, hydrogen sulphide is added to the liquor.

The process is operated as follows:

The sodium. carbonate content of the liquor is determined and lime is added in quantity theoretically sufiicient to convert the sodium carbonate to sodium hydroxide. Hydrogen sulphide, preferably in the form ofa gas, is then added to the liquor in quantity suflicient to convert the sodium hydroxide into sodium sulphide. By operating in this manner it is found that the removal of sodium carbonate is substantially complete and besides the yield of sodium sulphide from the liquor is increased by the amount formed by the action of hydrogen sulphide on the sodium hydroxide.

heir the reaction has been completed the solution which is now Substantially free from sodium carbonate is separated from the calcium carbonate precipitate. The sodium sulphide may then be recovered from.

the purified solution in a. comparatively pure state .by evaporation and crystallization.

While I have described my process as particularly designed for the treatment of dilute liquors resulting from the leaching of sodium sulphide black ash residues it will be apparent that the process is not limited to the treatment of dilute liquors obtained in this particular way. The process is very efl'ective for the removal of sodium carbon.

ate from concentrated solutions containing sodium sulphide and sodium carbonate and is of'course applicable to solutions of sodium sulphide containing sodium carbonate regardless of the source of such solutions or the manner in which they are formed.

Instead of treatin the liquors with lime and hydrogen sulphide, as described, I may treat .the liquors with calcium sulphide, preferably by adding to the liquors a slurr or solution of calcium sulphide. I I claim: 1. Process of purifying a sodium sulphide solution containing sodium carbonate which comprises addin to the solution lime and hydrogen sulphide.

.2. Process of removipg sodium carbonate from a solution containing the same and sodium sulphide which comprises causcioizing the solution with lime in quantity theoretically sufficient to convert the sodium carbonate to sodiuni hydroxide and adding 5 hydrogen sulphide to the solution in quantity sufiicient to convert the sodium hydroxide into sodium sulphide.

3. Process of purifying a solution of SOliHHll sulphide containing sodium carbonate which comprises converting the sodium ture HENRY HOWARD. 

